OBJECTIVE: We examined and characterized variation among NICUs in the use of vitamin A supplementation for the prevention of bronchopulmonary dysplasia in extremely low birth weight infants. METHODS: An historical cohort study of extremely low birth weight infants admitted within 7 days after birth to NICUs participating in the Pediatric Health Information System database, between January 1, 2005, and March 31, 2008, was performed. NICU medical directors were surveyed to determine attitudes and decision-making regarding adoption of vitamin A supplementation. The proportion of infants receiving vitamin A at each center was measured over time. Patient and hospital characteristics associated with vitamin A use were examined. RESULTS: Among 4184 eligible infants cared for in 30 NICUs, 1005 infants (24%) received vitamin A. Eighteen centers (60%) used vitamin A for some patients. Infants discharged in 2007 (odds ratio: 2.7 [95% confidence interval: 1.4-5.3]) and 2008 (odds ratio: 2.8 [95% confidence interval: 1.4-5.8]), compared with 2005, were more likely to receive vitamin A. NICU medical directors from centers using vitamin A, compared with centers that did not adopt vitamin A supplementation, reported stronger beliefs in the efficacy of vitamin A to reduce the incidence of bronchopulmonary dysplasia (83% vs 33%; P = .03) and in the ease with which vitamin A could be implemented (75% vs 22%; P = .02). CONCLUSIONS: Although the use of vitamin A is increasing, marked variation across NICUs remains. Provider attitudes and system characteristics seem to influence vitamin A adoption.